My 5 year relationship, help!

Okay, so heres the thing i've been with this girl for 5 years, and i love her like i really do love her The problem is we didnt start good, up till what i knew she was already with someone but we were friends i was young but somehow i proposed her to be my girlfriend we started at a goodpoint and things started getting messed up she told my cousins she likes the other guy too, so when i told her she somehow convinced me, this went on for almost two years until she finally left that guy She has suffered childhood trauma, which i think causes her to be this way or act this way, im not saying shes abnormal but i dont know what goes on with her Anyway ive caught her cheating with me alot of times, and it hasnt been cheating like completely being physical with someone its cheating as in telling that guy she has no boyfriend and than you know i love you babe i love you too and all of that Although while i returned to my home country once she did meet her ex and kissed her, but told me later on When i returned again to my home country now, its been 2 years and we fought alot, till that time she once again tried to cheat me with another guy and kept on doing it many times but whenever i tried to leave she would go anywhere just to get me back and say that she cant be without me and i dont know but she managed to convince me, now 1 week back she came to my home country for a treatment i went to meet her, she was taking my sister to meet her aunt and left her mobile, thinking i wouldnt be able to open the password, well i did and what i saw was she has been with this guy for almost one month, theyve met, hugged but that is till when i know, the problem is i tried being nice and i told her to move on and let me go, the thing is she just wouldnt let me go she hugged me started crying and you know what they do, my sister told me to message that guy and talk to him, i did but then i discussed with one of my friends he told me to leave the situation upto her, i did that too and thought not to talk to that guy but i already did message him, he did see after a day or two and asked her about all of this, we got into a fight the things she told me was really bad that she was getting engaged and he was going to come to his family but at the same time she denies this too, i told her to go but she just keeps coming back and telling me she cant live without me, she made me talk to that guy and tell him i was lying, this has become a huge problem for me. What i need is an advice on what to do? i love her its true and maybe she might too she has this problem whenever i leave she starts flirting with people and all of that. I dont want you to be negative against her or just tell me to move on, give me real advice think of it as every perspective, even hers Please i really need help as to what i should do next. We are still talking, i will meet her on sunday and i told her i need to discuss everything if anyone of you can advice please let me know.. Thank you

We both are 19 I dont know what the problem is, see we have been physical not till the intercourse but you get my point Ive tried being friends and letting her go, but she wont leave me, she keeps coming back i forgot to mention one thing, she keeps on saying i havent done much for her, honestly i have but yes i accept im not the ideal boyfriend Right now im asking her if she will leave that guy because she keeps on talking i gave her a deadline untill she is here in my home land, she keeps on saying i shouldnt expect anything until i come back but ive made up my mind if she leaves without breaking up with that guy i will move on